The proposed research will attempt to elucidate some aspects of chromosome movements in different stages of mitosis by a combination of light and electron microscopic investigations on selected single cells with biochemical and physiological studies on isolated spindles of two types (intact spindles and chromosome-free spindles, explained in proposal). The majority of experiments are designed to test key aspects of the applicants's new zipper hypothesis of chromosome movement: lateral MT association, MT movement caused by zipping. The proposed experiments aim eventually at understanding not only the mechanism, but the control of chromosomal and microtubular movments in intact and isolated spindles under physiological conditions. This goal will be approached in a series of experimental steps which progress logically from work on isolated MTs, to isolated chromosome-free spindles, and finally to intact mitotic spindles.